<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        /*body{margin:0;padding:0;outline:1px solid #afa;}
        span{display:block;margin:20px 20px;width:30px;height:30px;outline:1px solid #faa;border:10px solid #aae;}*/
    </style>
</head>
<body>
    <span id="span" class="see" style="color:#fcf;"></span>
    <script>
        var spanObj = document.getElementById('span');
        spanObj.setAttribute('my-data', 1);
        console.log(spanObj);
        console.log(typeof spanObj.getAttribute('my-data'));
        spanObj.onclick = function(){
            //body
        }
        spanObj.onclick = foo();
        function foo(){
            //body
        }
        spanObj.addEventListener(click,foo,false);
    </script>
</body>
</html>